Sea Level Variation And Its Effect On Storm Surge In The East China Sea

Sea level variation in the North Pacific Ocean during 1992 to 2008 was analyzed by the AVISO altimeter data, and their relationship with the Kuroshio current in representative regional area such as Kuroshio Extension (KE) and East China Sea (ECS) was given in this paper. Based on IPCC AR4 A1B scenario, we forecasted the sea level variation in 21^st century using CCSM model result and analyzed the effects of sea level variations on the storm surge along the coast of the East China Sea using a three-dimensional high-resolution hydrodynamic model (Ecomsed).Inter-annual sea level variation (3-5 year) and the long-term variation with the rising rate of 3.9 mm/yr are obvious in the North Pacific Ocean. Sea level in the North Pacific Ocean varies noticeably along Kuroshio area, such as Kuroshio Extension area and East China Sea. The second Empirical Orthogonal Functions (EOF) of the sea level variation in the KE is the Kuroshio meander mode with 27month quasi-biannual period. The sea level inter-annual variation in KE area relates to El Ni?o and Kuroshio current closely. The correlation coefficient between sea level inter-annual variation and El Ni?o is 0.74 in well-advanced meander year of 2002-2004. In up-stream area, the sea level variation with inter-annual period is affected by Kuroshio meander significantly. In well-advanced meander year, the sea level is higher in south of KE path, and the difference between the two sides of jet is larger. During no-meander period, the sea level difference between the two sides of jet is small, while KE weakens with the Kuroshio path migrating southward. In ECS, the sea level varies with obvious inter-annual variation and seasonal variation. The Rossby wave and geostrophic adjustment of Kuroshio are important factors on the variability of the sea level in Kuroshio area in the ECS. When the transport of the Kuroshio is large such as 1995-98, the sea level has a good connection with the Kuroshio current. While the transport of PN is smaller (2002-06), the sea level variation is concerned with the Rossby waves which carry the positive sea level from the interior ocean.The sea level in the 21^st century has obviously seasonal, inter-annual and inter-decadal variability under IPCC AR4 A1B scenario. Before 2060's, the sea level rise with 2.7 mm/yr, and fall with 4.8 mm/yr after then. The sea level reaches the peak in 2060's. The inter-annual variability of 4-8 year is significant in the middle of 21^st century, and at the beginning and the end of the 21^st century the sea level varies with inter-annual period of 2-3 year. The sea level rises before 2060's at KE and ECS area, and it maintains in high level during 2050-2060.And then, the sea level varies smoothly in the East China Sea, but in KE area the sea level declines remarkably.Sea level variations under SRES A1B scenario play a significant role on storm surge evolution in the East China Sea. The"SRES A1B scenario storm surge"combined with the relevant monthly sea level in the 2060 year in 21^st century was simulated by 1989-2008 typhoon cases. Before 0807# typhoon arrived, storm set-up occurred in tide ebbing, and increased to high value around the higher tidal water (HTW) until the typhoon system covered the gauges. Residual elevation difference performs 10 cm in the three tide gauges. The influence of sea level variations maps the geographical variability. The maximal residual elevation in the 21^st century would occur along the Fujian and Zhejiang province coast. The maximal residual elevation and check water levels change with the effect of the sea level variations. The maximal residual elevation will increase along the northern coastline of the Jiangsu province, and areas surrounding Bo Sea, where would be the more vulnerable area. The check water in the 21^st century became higher as sea level varying, especially in Zhejiang and Fujian province coast could reach 4.5 m.